Ohio and Pennsylvania voted for Democratic hopeful Barack Obama in the U.S. presidential election on Tuesday, U.S. TV networks projected.

Both the two states are key battleground states, nicknamed the "big three" together with Florida, with 41 electoral votes. Analysts here said that with Ohio and Pennsylvania going to Obama, McCain hardly has chance to win the race for White House.

The 41 electoral votes gave a substantial boost to Obama to become the first African American president in U.S. history.

Latest polls by the TV networks show that Obama has obtained 207 electoral votes, while McCain 129 votes. The victor needs 270 electoral votes to win the Electoral College and capture the presidency.

Supporters of U.S. Democratic presidential nominee Senator Barack Obama (D-IL) cheer while waiting for his arrival at an election night rally in Grant Park in Chicago Nov 4, 2008.[Xinhua Photo]

Under U.S. elections system, the president is determined not by the most votes nationally but by a majority of the Electoral College, which has 538 members. The number of electors is equal to a state's number of representatives (based on population) and senators (two per state) in the U.S. Congress. In addition, the District of Columbia has three Electoral College Votes.

Each state, except Maine and Nebraska, awards its votes to the candidate who gets the most votes in the state. Maine and Nebraska split them by congressional district.

The Election Day dawned as McCain, 72, faces an enormous task in trying to prevent 47-year-old first term senator Obama from winning the White House.

Supporters of Democratic presidential candidate Barack Obama cheer as they arrive at Grant Park on election day in Chicago, where later on election night Obama is to address a rally of more than one million people. [Xinhua/AFP Photo]

According to a pre-election tracking poll conducted by The Washington Post and ABC News, Obama leads McCain by nine percentage points and is ahead in enough states to push him well past the 270 electoral votes need to win.

McCain continues to campaign furiously in a swath of East Coast and Midwestern states in his final push in the hope of staving off defeat, but to keep the White House in Republican hands, he needs to hold virtually every competitive state as well as some in which Obama is leading.

Whoever wins the presidency will make history. Obama could become the first African American president in the nation's history. McCain, if elected, will be oldest president swearing in a first-term, while his running mate, Sarah Palin, will become the first woman vice president in U.S. history.

Also in Tuesday's general elections, the Democrats have seized four Senate seats from the Republicans, adding the seats they controlled up to 53 in the 100-seat legislative body, according to the TV networks. Thirty-five Senate seats were up for elections this year.

(Xinhua News Agency November 5, 2008)